Published 4:00 am, Friday, December 24, 1999

1999-12-24 04:00:00 PDT Washington -- It sounds like something out of an old sci-fi movie. But the plasmatron, a device under development for several years at the Massachusetts Institute of Technology, may one day help reduce smog- producing emissions from cars and other vehicles.

Researchers told a recent meeting of the American Physical Society that they had moved a significant step closer to taking the device from the laboratory to the highway.

He said the team plans to road- test the plasmatron within a year, after demonstrating recently that it can be installed on a commercial car engine. The team is planning to test the device on a bus.

The plasmatron, about the size of a wine bottle, works as a sort of onboard oil refinery to convert ordinary hydrocarbon fuel into a hydrogen-rich gas. That gas, when added in small amounts to the ordinary fuel from which it was made, produces a mixture that burns efficiently and cleanly. Researchers say that emissions of pollutants such as nitrogen oxide could be reduced tenfold by cars equipped with plasmatrons.

In principle, all the fuel in a tank could be converted to the hydrogen-rich gas. But since the conversion process takes energy, the researchers say it is more cost-effective to convert only a fraction of the fuel. The best results in the recent tests, conducted at the Oak Ridge National Laboratory in Tennessee, were achieved when 25 percent of the fuel was converted.

Inside a plasmatron, an arc of electricity ignites the fuel and surrounding air into a plasma -- a hot collection of charged atoms and electrons. The electrically charged plasma accelerates reactions that generate a hydrogen-rich gas. That gas can then be fed along with the ordinary, untreated gasoline to the combustion chambers in the engine.

The mix of hydrogen gas and gasoline is more readily combustible than ordinary gasoline alone, allowing the engine to burn gasoline more completely and with less pollution.

Engineers have known for years that adding hydrogen to fuel makes engines run more cleanly. There have been proposals to use hydrogen gas alone as a fuel, but developing the proper storage medium to carry sufficient amounts of the gas continues to be a challenge. The MIT researchers sidestep that problem by using the plasmatron to generate hydrogen using the car's normal fuel supply.

Plasmatrons traditionally have been used to produce hydrogen-rich gas for industrial applications such as metals processing. Those devices have been quite large -- about the size of a car engine -- and impractical for improving automotive emission performance. The MIT team has come up with a much more compact design and recently tested it for two weeks on a car engine at Oak Ridge.

Alexander Rabinovich, an engineer at MIT, said the device ran reliably for four to six hours a day with no deterioration. The researchers found a marked reduction in emission of pollutants during the tests.

Nitrogen oxide emissions were cut more than a hundredfold, from an average of 2,700 parts per million without the plasmatron to 20 parts per million with the device. The reductions are not expected to be as dramatic in standard cars equipped with catalytic converters, but the MIT researchers said the goal of a tenfold reduction in nitrogen oxide emissions seems feasible.

The MIT researchers estimate that plasmatrons could be manufactured for commercial use for $200 to $300 each. The only component that would require replacement, an electrode, is cheap and easily changed.

The plasmatron could be tucked anywhere between the gas tank and the engine, where it would divert some of the fuel for refining into the hydrogen-rich gas before sending it along to the engine for burning with untreated fuel. In theory, the researchers say, the plasmatron could process any sort of "biocrude" carbon-containing oils -- including vegetable oils -- into hydrogen-rich fuel for vehicles. But processing of the cruder fuels requires too much energy for now.